Internal combustion engines employed in modern vehicles commonly include control modules operably connected to the engine's distributor and for controlling the distribution of spark to the spark plugs. The ignition control modules comprise micro-computer circuits adapted to control engine timing, these circuits being incased in a thermoplastic block. More specifically, the micro-computer circuits are used in controlling the electrical current from the coil of the ignition system to the distributor and in controlling the variation of the ignition dwell in response to engine speed. For example, the control modules may provide for a 15.degree. dwell at 700 rpm and 30.degree. to 32.degree. dwell at 2000 rpm.
It has been found that engine failure may often be attributed to failure of the control modules, and such failure occurrs particularly in engines operating under heavy loads such as in military vehicles or in emergency vehicles.